/*  $OpenBSD: freopen.c,v 1.9 2005/08/08 08:05:36 espie Exp $ */
/************************************************************************
 * Copyright (c) 1990, 1993
 *  The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 ************************************************************************/


#define __USE_BSD

#include "sys/stat.h"
#include "fcntl.h"
#include "unistd.h"
#include "stdio.h"
#include "stdlib.h"
#include "local.h"
#include "string.h"
#include <errno.h>


/*
 * Re-direct an existing, open (probably) file to some other file.
 * ANSI is written such that the original file gets closed if at
 * all possible, no matter what.
 */
FILE *
freopen(const char *file, const char *mode, FILE *fp)
{
    int f;
    int flags, isopen, oflags, sverrno, wantfd;

    if ((flags = __sflags(mode, &oflags)) == 0) {
        (void) fclose(fp);
        return ((FILE *)NULL);
    }

    if ((fp == stdout) && !(strncmp(file,"/dev/console",(sizeof("/dev/console") - 1))))
    {
        flags |= __SLBF;
    }
    else if ((fp == stderr) && !(strncmp(file,"/dev/console",(sizeof("/dev/console") - 1))))
    {
        flags |= __SNBF;
    }

    if (!__sdidinit_flag)
        __sinit();

    FLOCKFILE(fp);

    /*
     * There are actually programs that depend on being able to "freopen"
     * descriptors that weren't originally open.  Keep this from breaking.
     * Remember whether the stream was open to begin with, and which file
     * descriptor (if any) was associated with it.  If it was attached to
     * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
     * should work.  This is unnecessary if it was not a Unix file.
     */
    if (fp->_flags == 0) {
        fp->_flags = __SEOF;    /* hold on to it */
        isopen = 0;
        wantfd = -1;
    } else {
        /* flush the stream; ANSI doesn't require this. */
        if (fp->_flags & __SWR)
            (void) __sflush(fp);
        /* if close is NULL, closing is a no-op, hence pointless */
        isopen = fp->_close != NULL;
        if ((wantfd = fp->_file) < 0 && isopen) {
            (void) (*fp->_close)(fp->_cookie);
            isopen = 0;
        }
    }

    /* Get a new descriptor to refer to the new file. */
    f = open(file, oflags, DEFFILEMODE);
    if (f < 0 && isopen) {
        /* If out of fd's close the old one and try again. */
        if (errno == ENFILE || errno == EMFILE) {
            (void) (*fp->_close)(fp->_cookie);
            isopen = 0;
            f = open(file, oflags, DEFFILEMODE);
        }
    }
    sverrno = errno;

    /*
     * Finish closing fp.  Even if the open succeeded above, we cannot
     * keep fp->_base: it may be the wrong size.  This loses the effect
     * of any setbuffer calls, but stdio has always done this before.
     */
    if (isopen && f != wantfd)
        (void) (*fp->_close)(fp->_cookie);
    if (fp->_flags & __SMBF)
        free((char *)fp->_bf._base);
    fp->_w = 0;
    fp->_r = 0;
    fp->_p = (unsigned char *)NULL;
    fp->_bf._base = (unsigned char *)NULL;
    fp->_bf._size = 0;
    fp->_lbfsize = 0;
    if (HASUB(fp))
        FREEUB(fp);
    _UB(fp)._size = 0;
    WCIO_FREE(fp);
    if (HASLB(fp))
        FREELB(fp);
    fp->_lb._size = 0;

    if (f < 0) {            /* did not get it after all */
        fp->_flags = 0;     /* set it free */
        FUNLOCKFILE(fp);
        errno = sverrno;    /* restore in case _close clobbered */
        return ((FILE *)NULL);
    }

    /*
     * If reopening something that was open before on a real file, try
     * to maintain the descriptor.  Various C library routines (perror)
     * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
     */
    if (wantfd >= 0 && f != wantfd) {
        if (dup2(f, wantfd) >= 0) {
            (void) close(f);
            f = wantfd;
        }
    }

    fp->_flags = flags;
    fp->_file = f;
    fp->_cookie = fp;
    fp->_read = __sread;
    fp->_write = __swrite;
    fp->_seek = __sseek;
    fp->_close = __sclose;

    /*
     * When opening in append mode, even though we use O_APPEND,
     * we need to seek to the end so that ftell() gets the right
     * answer.  If the user then alters the seek pointer, or
     * the file extends, this will fail, but there is not much
     * we can do about this.  (We could set __SAPP and check in
     * fseek and ftell.)
     */
    if (oflags & O_APPEND)
        (void) __sseek((void *)fp, (fpos_t)0, SEEK_END);
    FUNLOCKFILE(fp);
    return (fp);
}
